PROCESS TO MANUFACTURE 2-CHLORO-1,1,1,2-TETRAFLUOROPROPANE (HCFC-244bb)

ABSTRACT

The invention provides an improved process to manufacture 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) by reacting 2-chloro-3,3,3,-trifluoropropene (HCFO-1233x1) with hydrogen fluoride, in a liquid phase reaction in the presence of hydrogen chloride and a liquid phase fluorination catalyst. The hydrogen chloride is added into the reaction from an external source at a pressure of about 100 psig or more. The HCFC-244bb is an intermediate in the production of 2,3,3,3-tetrafluoropropene-1 (HFO-1234yf).

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 14/936,160,filed Nov. 9, 2015, which application is a division of U.S. applicationSer. No. 14/021,256, filed Sep. 9, 2013, (now U.S. Pat. No. 9,181,151,issued Nov. 10, 2015) which application is a continuation of U.S.application Ser. No. 12/512,955, filed Jul. 30, 1999 (now U.S. Pat. No.8,664,455, issued Mar. 4, 2014), which application claims the benefit ofU.S. Provisional Patent Application Ser. No. 61/087,206 filed Aug. 8,2008, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an improved process for manufacturing2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb), or more particularlyto an improved process for the production of HCFC-244bb by reacting2-chloro-3,3,3,-trifluoropropene (HCFO-1233xf) with hydrogen fluoride,in a liquid phase reaction vessel in the presence of hydrogen chlorideand a liquid phase fluorination catalyst. The HCFC-244bb is anintermediate in the production of 2,3,3,3-tetrafluoropropene(HFO-1234yf) which is a refrigerant with low global warming potential.

Description of the Related Art

Fluorocarbon based fluids have found widespread use in industry in anumber of applications, including as refrigerants, aerosol propellants,blowing agents, heat transfer media, and gaseous dielectrics. Because ofthe suspected environmental problems associated with the use of some ofthese fluids, including the relatively high global warming potentialsassociated therewith, it is desirable to use fluids having the lowestpossible greenhouse warming potential in addition to zero ozonedepletion potential. Thus there is considerable interest in developingenvironmentally friendlier materials for the applications mentionedabove. Tetrafluoropropenes, having zero ozone depletion and low globalwarming potential, have been identified as potentially filling thisneed. However, the toxicity, boiling point, and other physicalproperties in this class of chemicals vary greatly from isomer toisomer. One tetrafluoropropene having valuable properties is2,3,3,3-tetrafluoropropene (HFO-1234y0. HFO-1234yf has been found to bean effective refrigerant, heat transfer medium, propellant, foamingagent, blowing agent, gaseous dielectric, sterilant carrier,polymerization medium, particulate removal fluid, carrier fluid, buffingabrasive agent, displacement drying agent and power cycle working fluid.Thus, there is a need for new manufacturing processes for the productionof tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene.

In U.S. Pat. No. 2,931,840, methyl chloride has been pyrolyzed alongwith CF₂HCl at 800° C. to give a product stream that contains about 15%of CF₃CF═CH₂. HFO-1234yf has also been made by the dehydrofluorinationof CF₃CHFCH₂F with KOH in butyl ether (Chem. Abstr. 1961: 3490, and bythe reaction of CF₃CF₂CH₂OH with hydrogen in U.S. Pat. No. 4,900,874.

It would be advantageous to have a process for the manufacture ofHFO-1234yf that is continuous, and which uses readily available rawmaterials. As the prior art processes fail in one or more of thesedesirable features, more advantageous routes are desired, especiallythose amenable to large-scale manufacture.

One of the steps in recent manufacturing processes for HFO-1234yfrequires the fluorination HCFO-1233xf with hydrogen fluoride to form2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb). In the liquid phasefluorination of HCFO-1233xf to produce HCFC-244bb, no 1-1Cl is producedbecause the reaction is strictly a hydrofluorination reaction where HFadds across the double bond. This lack of HC1 by-product formation isunique when compared to other well-known liquid phase fluorinationreactions that produce CFCs (e.g. CFC-12), HCFCs (e.g. HCFC-22,HCFC-142b), and HFCs (e.g. HFC-143a, HFC-245fa). This is because thesereactions involve a halogen exchange, in whole or in part. That is, F⁻replaces a Cl⁻ on the molecule. It is advantages to run liquid phasefluorination reactions at relatively elevated pressures which are easilyachieved by the formation of HCl. Because it is non-condensable at thedesired reaction conditions, HCl formation also increases mixing in thereactor and it readily comes out in the overhead of the catalyststripper and helps by carrying out the fluorinated product. Because noHCl is produced in the reaction of HCFO-1233xf to HCFC-244bb there isless mixing in the reactor which may decrease conversion and promoteby-product formation. In addition, the reactor is more difficult tocontrol because there is no HCl to create high pressure nor to helpcarry out the HCFC-244bb that is formed.

In the present invention HCl is co-fed to the reactor along with the HFand HCFO-1233xf. The reactor and catalyst stripper runs like a typicalliquid phase fluorination reaction that produce CFCs, HCFC's, and HFCsas described above. This has a number of benefits. It enables thereaction to achieve and run at relatively elevated pressures, itincreases mixing in the reactor, and it readily leaves the reactor inthe overhead of the catalyst stripper carrying with it productHCFC-244bb. The HCl co-feed is essentially inert, does not participatein the fluorination reaction, and produces little or no unwantedby-products. Any source of HCl can be used in the reaction. PreferablyHCl produced in-situ from a prior step in a multi-step process toproduce HFO-1234yf is used as the source. An example of such a stepinvolves the fluorination of 1,1,2,3-tetrachloropropene or1,1,1,2,3-pentachloropropane with HF, optionally but preferably in thepresence of a fluorination catalyst to form HCFO-1233xf intermediate andHCl. Then, all or only a portion of the HCl produced in this step isco-fed into the liquid phase fluorination reactor that producesHCFC-244bb.

SUMMARY OF THE INVENTION

The invention provides a process for the production of2-chloro-1,1,1,2-tetrafluoropropane which comprises reacting2-chloro-3,3,3,-trifluoropropene with hydrogen fluoride, in a liquidphase reaction vessel in the presence of hydrogen chloride and a liquidphase fluorination catalyst, wherein the hydrogen chloride is added intothe reaction from an external source at a pressure of about 100 psig ormore.

The invention also provides a process for the production of2,3,3,3-tetrafluoropropene which comprises (i) continuously reacting2-chloro-3,3,3,-trifluoropropene with hydrogen fluoride, in a liquidphase reaction and co-feeding hydrogen chloride, in the presence of aliquid phase fluorination catalyst to produce a composition comprising2-chloro-1,1,1,2-tetrafluoropropane, wherein the hydrogen chloride isadded into the reaction from an external source at a pressure of about100 psig or more; and then

-   (ii) dehydrohalogenating the 2-chloro-1,1,1,2-tetrafluoropropane    under conditions effective to produce 2,3,3,3-tetrafluoropropene.-   The invention also provides a process for the production of    2,3,3,3-tetrafluoropropene which comprises-   a) fluorinating 1,1,2,3-tetrachloropropene to produce    2-chloro-3,3,3,-trifluoropropene;-   b) reacting the 2-chloro-3,3,3,-trifluoropropene with hydrogen    fluoride, in a liquid phase reaction and co-feeding hydrogen    chloride, in the presence of a liquid phase fluorination catalyst to    produce a composition comprising    2-chloro-1,1,1,2-tetrafluoropropane, wherein the hydrogen chloride    is added into the reaction from an external source at a pressure of    about 100 psig or more; and then-   c) dehydrohalogenating the 2-chloro-1,1,1,2-tetrafluoropropane under    conditions effective to produce 2,3,3,3-tetrafluoropropene.

DESCRIPTION OF THE INVENTION

The first step in the process for the production of2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) requires reacting2-chloro-3,3,3,-trifluoropropene (HCFO-1233x0 with hydrogen fluoride, ina liquid phase reaction vessel in the presence of hydrogen chloride anda liquid phase fluorination catalyst to thereby produce HCFC-244bb.Preferably the reaction is conducted continuously.

HCFO-1233xf is an intermediate in the production of2,3,3,3-tetrafluoropropene (HFO-1234yf) which is well known in the artas described in U.S. Applications 20070007488 and 20070197842, thespecifications of which are incorporated herein by reference. In amethod of preparing HCFO-1233xf, precursor reagents are fluorinated withhydrogen fluoride. This may be done, for example, by the gas or liquidphase catalytic fluorination of CCl₂═CClCH₂Cl with HF to yieldHCFO-1233xf. The reaction products of such precursors includeHCFO-1233xf, unreacted HF, HCl, and other by-products which are thenavailable for separation into component parts.

In the practice of the present invention, a liquid phase catalyst asdescribed below is charged into a fluorination reactor prior to heatingthe reactor. Any reactor suitable for a fluorination reaction may beused in the invention. Preferably the reactor is constructed frommaterials which are resistant to the corrosive effects of HF such asHastelloy-C, Inconel, Monel and fluoropolymer-lined vessels. Such liquidphase fluorination reactors are well known in the art. Then the HF, HCland the HCFO-1233xf are fed to the reactor after the reactor reaches thedesired temperature. In the preferred embodiment, the reaction isconducted at a temperature of from about 30° C. to about 200° C., morepreferably from about from about 50° C. to about 150° C., and still morepreferably from about 75° C. to about 125° C. The pressure of thereaction varies depending on the temperature, quantity of hydrogenchloride and hydrogen fluoride used, and conversion of HCFO-1233xf.Convenient operating pressure ranges from about 5 psia to about 200psia, and preferably from 30 to about 175 psia, and most preferablyabout 60 psia to about 150 psia.

In the preferred embodiment, the catalyst is present in an amount offrom about 2% to about 80%, and preferably from about 5% to about 50%,and most preferably from about 10% to about 20%, based on the molepercent of HCFO-1233xf. Fluorination catalysts having a purity of atleast 98% are preferred.

Based on reaction stoichiometry, the required mole ratio of HF toHCFO-1233xf is at least equal to the number of double bonds in thestarting organic material and preferably is present in an excess. In thepreferred embodiment, the mole ratio of HF to HCFO-1233xf ranges from atleast about 1:1 to about 50:1, more preferably from about 1:1 to about30:1 and most preferably from about 2:1 to about 15:1. Any water in theHF will react with and deactivate the catalyst. Therefore substantiallyanhydrous HF is preferred. By “substantially anhydrous” is meant thatthe HF contains less than about 0.05 weight % water and preferablycontains less than about 0.02 weight % water. However, one of ordinaryskill in the art will appreciate that the presence of water in thecatalyst can be compensated for by increasing the amount of catalystused. HF suitable for use in the reaction may be purchased fromHoneywell International Inc. of Morristown, N.J.

The liquid phase fluorination reaction is conducted with a sufficientamount of hydrogen chloride to elevate the pressure in the reactor,above the pressure achieved compared to a similar liquid phase reactionwithout adding hydrogen chloride. In the preferred embodiment, the moleratio of HCl to HCFO-1233xf ranges from about 0.1:1 to about 10:1, morepreferably from about 1:1 to about 5:1 and most preferably from about1:1 to about 3:1. The hydrogen chloride is added into the reaction froman external source at a pressure of about 100 psig or more; preferablyfrom about 100 psig to about 500 psig, and more preferably from about120 psig to about 300 psig.

Any liquid phase fluorination catalyst may be used in the invention. Anon-exhaustive list include Lewis acids, transition metal halides,transition metal oxides, Group Vb metal halides, a Group Vb metalhalides, or combinations thereof. Non-exclusive examples of liquid phasefluorination catalysts are an antimony halide, a tin halide, a tantalumhalide, a titanium halide, a niobium halide, and molybdenum halide, aniron halide, a fluorinated chrome halide, a fluorinated chrome oxide orcombinations thereof. Specific non-exclusive examples of liquid phasefluorination catalysts are SbCl₅, SbCl₃, SbF₅, SnCl₄, TaCl₅, TiCl₄,NbCl₅, MoCl₆, FeCl₃, CrF₃, Cr₂O₃, a fluorinated species of SbCl₅, afluorinated species of SbCl₃, a fluorinated species of SnCl₄, afluorinated species of TaCl₅, a fluorinated species of TiCl₄, afluorinated species of NbCl₅, a fluorinated species of MoCl₆, afluorinated species of FeCl₃, a fluorinated species of Cr₂O₃, orcombinations thereof. Liquid phase fluorination catalyst comprisesSbCl₅, SbCl₃, SbF₅, SnCl₄, TaCl₅, TiCl₄, NbCl₅, MoCl₆, FeCl₃, CrF₃,Cr₂O₃, a fluorinated species of SbCl₅, a fluorinated species of SbCl₃, afluorinated species of SnCl₄, a fluorinated species of TaCl5, afluorinated species of TiCl₄, a fluorinated species of NbCl₅, afluorinated species of MoCl₆, a fluorinated species of FeCl₃, afluorinated species of Cr₂O₃, or combinations thereof.

These catalysts can be readily regenerated by any means known in the artif they become deactivated. One suitable method of regenerating thecatalyst involves flowing a stream of chlorine through the catalyst. Forexample, from about 0.002 to about 0.2 lb per hour of chlorine can beadded to the liquid phase reaction for every pound of liquid phasefluorination catalyst. This may be done, for example, for from about 1to about 2 hours or continuously at a temperature of from about 65° C.to about 100° C.

The resulting HCFC-244bb, as well as HF and HCl may be recovered fromthe reaction mixture via any separation or purification method known inthe art such as neutralization and distillation. The HCFC-244bb can beused in pure form, or optionally in partially pure form or impure formwith the entire effluent from the HCFC-244bb production step used as anintermediate in the production of 2,3,3,3-tetrafluoropropene HFO-1234yf.The process of the invention may be carried out either in a batch orcontinuous mode. In a continuous process, the HCFO-1233xf, HCl and HFare preferably fed simultaneously to the reactor after the reactorreaches the desired temperature. The temperature and pressure of thefluorination reaction remain essentially the same for both the batch andcontinuous modes of operation. The residence time or contact time,varies from about 1 second to about 2 hours, preferably from about 5seconds to about 1 hour and most preferably from about 10 seconds toabout 30 minutes. A sufficient quantity of catalyst must be present toeffect the fluorination in the residence times described above. In acontinuous mode of operation, HF, HCFC-244bb and hydrogen chloride arecontinuously removed from the reactor.

In a preferred embodiment, the invention relates to a multistep processin which the above described process to produce HCFC-244bb isimmediately preceded by a prior process step for producing2-chloro-3,3,3,-trifluoropropene (HCFO-1233x1) by vapor phasefluorination of 1,1,2,3,-tetrachloropropene (HCC-1230xa) or1,1,1,2,3-tetrachloropropane (HCC-240db) with hydrogen fluoride toproduce a stream comprising hydrogen fluoride,2-chloro-3,3,3,-trifluoropropene, and hydrogen chloride. Preferably all,and more preferably at least a part of this stream is directly fed tothe liquid phase reaction to make HCFC-244bb.

This reaction may be conducted in any reactor suitable for a vapor orliquid phase fluorination reaction. Preferably the reactor isconstructed from materials which are resistant to the corrosive effectsof hydrogen fluoride and catalyst such as Hastalloy, Inconel, Monel andvessels lined with fluoropolymers. In case of a vapor phase process, thereactor is filled with a vapor phase fluorination catalyst. Anyfluorination catalysts known in the art may be used in this process.Suitable catalysts include, but are not limited to chromium, aluminum,cobalt, manganese, nickel and iron oxides, hydroxides, halides,oxyhalides, inorganic salts thereof and their mixtures. Combinations ofcatalysts suitable for the present invention nonexclusively includeCr₂O₃, Cr₂O₃/Al₂O₃, Cr₂O₃/AlF₃, Cr₂O₃/carbon, CoCl₂O₃/Al₂O₃,NiCl₂Cr₂O₃/Al₂O₃, CoCl₂/AlF₃, NiCl₂/AlF₃ and mixtures thereof. Chromiumoxide/aluminum oxide catalysts are described in U.S. Pat. No. 5,155,082which is incorporated herein by reference. Chromium (III) oxides such ascrystalline chromium oxide or amorphous chromium oxide are preferredwith amorphous chromium oxide being most preferred. Chromium oxide(Cr₂O₃) is a commercially available material which may be purchased in avariety of particle sizes. Fluorination catalysts having a purity of atleast 98% are preferred. The fluorination catalyst is present in anexcess but in at least an amount sufficient to drive the reaction.

The reactor is preheated to the fluorination reaction temperature whileanhydrous HF is fed to the reactor. The 1,1,2,3,-tetrachloropropene(HCC-1230xa) or 1,1,1,2,3-tetrachloropropane (HCC-240db) and HF may befed to the reactor at any convenient temperature and pressure. In apreferred embodiment either or both of the HCC-1230xa or HCC-240db andthe HF are pre-vaporized or preheated to a temperature of from about 30°C. to about 300° C. prior to entering the reactor. In anotherembodiment, the HCC-1230xa or HCC-240db and HF are vaporized in thereactor. The HF and HCC-1230xa or HCC-240db feeds are then adjusted tothe desired mole ratio. The HF to HCC-1230xa or HCC-240db mole ratiopreferably ranges from about 3:1 to about 100:1; more preferably fromabout 4:1 to about 50:1 and most preferably from about 5:1 to about20:1.

The vapor phase fluorination reaction is conducted at a preferredtemperature ranging from about 80° C. to about 400° C.; more preferablyfrom about 100° C. to about 350° C. and most preferably from about 200°C. to about 330° C. Reactor pressure is not critical and can besuperatmospheric, atmospheric or under vacuum. The vacuum pressure canbe from about 5 ton (0.0966 psig) to about 760 torr (14.69 psig). Duringthe vapor phase fluorination reaction, HCC-1230xa or HCC-240db and HFare reacted in a vapor phase in the presence of the fluorinationcatalyst. The reactant vapor is allowed to contact the fluorinationcatalyst for from about 1 to 120 seconds or more preferably from about 1to 20 seconds. For purposes of this invention, “contact time” is thetime required for the gaseous reactants to pass through the catalyst bedassuming that the catalyst bed is 100% void.

In the preferred embodiment, the process flow is in the down directionthrough a bed of the catalyst. Before each use, the catalyst ispreferably dried, pre-treated and activated. It may also be advantageousto periodically regenerate the catalyst after prolonged use while inplace in the reactor. Pre-treatment can be done by heating the catalystto about 250° C. to about 430° C. in a stream of nitrogen or other inertgas. The catalyst may then be activated by treating it with a stream ofHF diluted with a large excess of nitrogen gas in order to obtain highcatalyst activity. Regeneration of the catalyst may be accomplished byany means known in the art such as using an oxidizing agent such as 02or chlorine. For example, passing air or air diluted with nitrogen overthe catalyst at temperatures of from about 100° C. to about 400° C.,preferably from about 200° C. to about 375° C., for from about 8 hoursto about 3 days, depending on the size of the reactor.

In one embodiment, the HCFO-1233xf may be recovered from thefluorination reaction product mixture comprised of unreacted startingmaterials, by-products including HC1, HF, and the HCFO-1233xf by anymeans known in the art, such as by distillation. For example, thedistillation may be preferably conducted in a standard distillationcolumn at a pressure which is less than about 300 psig, preferably lessthan about 200 psig and most preferably less than 150 psig. The pressureof the distillation column inherently determines the distillationoperating temperature. HCl may be recovered by operating thedistillation column at from about −40° C. to about 25° C., preferablyfrom about −40° C. to about −20° C. HCFO-1233xf may be recovered byoperating the distillation column at from about −10° C. to about 60° C.Single or multiple distillation columns may be used. The distillateportion includes substantially all the HCl, and HCFO-1233xf produced inthe reaction and the bottoms portion includes the HF and otherimpurities.

However, in a more preferred embodiment, the product stream from thisstep comprising HCFO-1233xf, HCl and HF is fed from the vapor phasefluorination reaction directly into the liquid phase reaction describedabove, which converts the HCFO-1233xf into the HCFC-244bb.

In another embodiment, the HCFC-244bb produced is thendehydrohalogenated under conditions effective to produce2,3,3,3-tetrafluoropropene (HFO-1234yf). Preferably thedehydrohalogenating step comprises a gas or vapor phase catalyticreaction.

The catalytic conversion of HCFC-244bb is conducted under conditionseffective to dehydrochlorinate HCFC-244bb to produce2,3,3,3-tetrafluoropropene (HFO-1234yf. Preferably dehydrochlorinationof HCFC-244bb is done in a vapor phase, and more preferably in afixed-bed reactor in the vapor phase. The dehydrohalogenation reactionmay be conducted in any suitable reaction vessel or reactor, but itshould preferably be constructed from materials which are resistant tothe corrosive effects of hydrogen chloride (to the extent that suchmaterial is formed under the dehydrohalogenation conditions) such asnickel and its alloys, including Hastelloy, Inconel, Incoloy, and Monelor vessels lined with fluoropolymers and may employ single or multipletubes packed with a dehydrohalogenation catalyst.

Catalysts for HCFC-244bb Dehydrochlorination to HFO-1234yf

The catalysts may be metal halides, halogenated metal oxides, neutral(or zero oxidation state) metal or metal alloy, or activated carbon inbulk or supported form. When metal halides or metal oxides catalysts areused, preferably mono-, bi-, and tri-valent metal halides, oxide andtheir mixtures/combinations, and more preferably mono-, and bi-valentmetal halides and their mixtures/combinations. Component metals include,but are not limited to, Cr³⁺, Fe³⁺, Mg²⁺, Ca²⁺, Ni²⁺, Zn²⁺, Pd²⁺, Li⁺,Na⁺, K⁺, and Cs⁺. Component halogens include, but are not limited to,F⁻, Br⁻, and P. Examples of useful mono- or bi-valent metal halideinclude, but are not limited to, LiF, NaF, KF, CsF, MgF₂, CaF₂, LiCl,NaCl, KCl, and CsCl. Halogenation treatments can include any of thoseknown in the prior art, particularly those that employ HF, F₂, HCl, Cl₂,HBr, Br₂, HI, and I₂ as the halogenation source.

When neutral, i.e., zero valent, metals, metal alloys and their mixturesare used. Useful metals include, but are not limited to, Pd, Pt, Rh, Fe,Co, Ni, Cu, Mo, Cr, Mn, and combinations of the foregoing as alloys ormixtures. The catalyst may be supported or unsupported. Useful examplesof metal alloys include, but are not limited to, SS 316, Monel 400,Inconel 825, Inconel 600, and Inconel 625.

The HCFC-244bb is introduced into the reactor either in pure form,partially purified form, or as part of the reactor effluent from thepreceding step. The HCFC-244bb may optionally be fed with an inert gasdiluent such as nitrogen, argon, or the like. In a preferred embodimentof the invention, the HCFC-244bb is pre-vaporized or preheated prior toentering the reactor. Alternately, the HCFC-244bb is vaporized insidethe reactor. Useful reaction temperatures may range from about 100° C.to about 700° C. Preferred temperatures may range from about 150° C. toabout 600° C., and more preferred temperatures may range from about 200°C. to about 550° C. The reaction may be conducted at atmosphericpressure, super-atmospheric pressure or under vacuum. The vacuumpressure can be from about 5 ton (0.0966 psig) to about 760 ton (14.69psig). Contact time of the HCFC-244bb with the catalyst may range fromabout 0.5 seconds to about 120 seconds, however, longer or shorter timescan be used.

Preferably in such dehydrofluorination embodiments as described in thissection, the conversion of the HCFC-244bb is at least about 10%, morepreferably at least about 20%, and even more preferably at least about30%. Preferably in such embodiments, the selectivity to HFO-1234yf, isat least about 70%, more preferably at least about 85% and morepreferably at least about 95%.

In the preferred embodiment, the process flow is in the down or updirection through a bed of the catalyst. It may also be advantageous toperiodically regenerate the catalyst after prolonged use while in placein the reactor. Regeneration of the catalyst may be accomplished by anymeans known in the art such as using an oxidizing agent such as O₂ orchlorine. For example, by passing air or air diluted with nitrogen overthe catalyst at temperatures of from about 100° C. to about 400° C.,preferably from about 200° C. to about 375° C., for from about 0.5 hourto about 3 days depending on the size of the reactor.

In general, the effluent from the dehydrohalogenation reaction step,including any intermediate effluents that may be present in multi-stagereactor arrangements, may be processed to achieve desired degrees ofseparation and/or other processing. For example, in embodiments in whichthe reactor effluent comprises HFO-1234yf, the effluent will generallyalso include HC1 and unreacted HCFC-244bb. Some portion or substantiallyall of these components of the reaction product may be recovered fromthe reaction mixture via any separation or purification method known inthe art such as neutralization and distillation. It is expected thatunreacted HCFC-244bb could be recycled, completely or partially, toimprove the overall yield of the desired CF₃CF═CH₂ (HFO-1234yf).Optionally but preferably, hydrogen chloride is then recovered from theresult of the dehydrochlorination reaction. Recovering of hydrogenchloride is conducted by conventional distillation where it is removedfrom the distillate.

Alternatively, HCl can be recovered or removed by using water or causticscrubbers. When a water extractor is used HCl is removed as an aqueoussolution. When caustic is used, HCl is just removed from system as achloride salt in aqueous solution.

In an alternate embodiment of the invention, dehydrohalogenation ofHCFC-244bb can also be accomplished by reacting it with a strong causticsolution that includes, but is not limited to KOH, NaOH, Ca(OH)₂ and CaOat an elevated temperature. In this case, the strength of the causticsolution is of from about 2 wt % to about 100 wt %, more preferably fromabout 5 wt % to about 90 wt % and most preferably from about 10 wt % toabout 80 wt %. The caustic to HCFC-244bb mole ratio preferably rangesfrom about 1:1 to about 2:1; more preferably from about 1.1:1 to about1.5:1 and most preferably from about 1.2:1 to about 1.4:1. The reactionmay be conducted at a temperature of from about 20° C. to about 100° C.,more preferably from about 30° C. to about 90° C. and most preferablyfrom about 40° C. to about 80° C. As above, the reaction may beconducted at atmospheric pressure, super-atmospheric pressure or undervacuum. The vacuum pressure can be from about 5 torr (0.0966 psig) toabout 760 torr (14.69 psig). In addition, a solvent or phase transfercatalyst such as Aliquat 336 may optionally be used to help dissolve theorganic compounds in the caustic solution. This optional step may beconducted using solvents that are well known in the art for saidpurpose. Thereafter, HFO-1234yf may be recovered from the reactionproduct mixture comprised of unreacted starting materials andby-products by any means known in the art, such as by extraction andpreferably distillation. The mixture of HFO-1234yf and any by-productsare passed through a distillation column. For example, the distillationmay be preferably conducted in a standard distillation column atatmospheric pressure, super-atmospheric pressure or a vacuum. Preferablythe pressure is less than about 300 psig, preferably less than about 200psig and most preferably less than 150 psig. The pressure of thedistillation column inherently determines the distillation operatingtemperature. Preferably in such dehydrofluorination embodiments asdescribed in this section, the conversion HCFC-244bb is at least about60%, more preferably at least about 75%, and even more preferably atleast about 90%. Preferably in such embodiments, the selectivity toHFO-1234yf, is at least about 70%, more preferably at least about 85%and more preferably at least about 95%.

The following non-limiting examples serve to illustrate the invention.

EXAMPLE 1

A continuous liquid phase fluorination of the2-chloro-3,3,3-trifluoropropene(HCFO-1233xf)+HF→2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) indemonstrated while continuously feeding HCl. The fluorination catalystfor the experiment is SbCl₅.

6500 grams of SbCl5 are contained in a Teflon™-lined liquid phasereactor (Teflon is a trademark of E.I. duPont de Nemours & Co) equippedwith a catalyst stripper, 2-inch ID (inside diameter) packed column andwith a condenser whose function is to return entrained catalyst, some ofthe unreacted HF and some of the unreacted HCFO-1233xf to the reactorwhen the system is running in continuous reaction mode. The reactor is2.75-inch ID×36-inch L (length) and is not equipped with amixer/agitator. The reactor is heated to about 85° C.-87° C. Thecatalyst is then activated by the addition of 1500 grams of HF followedby 1500 grams of Cl₂. HCl generated by the fluorination of the catalystraises the reaction system pressure to about 100 psig where it iscontrolled. The continuous gaseous HF feed is started first. It isbubbled into the liquid catalyst through a dip tube at a rate of 1.1lb/hr, and when 1.0 lbs of HF has been added, the gaseous HCl and2-chloro-3,3,3-trifluoropropene feeds are started. They also enter theliquid catalyst by way of a dip tube. The HCl and HCFO-1233xf are fedcontinuously at rates of 0.56 lb/hr and 1.0 lb/hr respectively. The moleratio of HF to 1233xf is 7.1:1 and the mole ratio of HCl to 1233xf is2:1. The reaction temperature is maintained at 85-87° C. and thepressure is maintained at 100 psig. The HCl is gaseous at theseconditions and is inert (i.e. does not react). As it bubbles into theliquid reaction mixture it dramatically increases mixing and because ofhigh vapor pressure it helps to maintain the reactor pressure. It exitsthe reaction system through the top of the catalyst stripper helping tocarry out the reaction product, HCFC-244bb with it. The experiment isrun continuously for 50 hours. The average conversion of HCFO-1233xf forthe run is >99% and the selectivity to 244bb reaches 98%.

EXAMPLE 2

The stream exiting the top of the catalyst stripper in Example 1containing mainly HCFC-244bb, unreacted HF, and HCl is fed to aconventional distillation column where HCl is recovered and/or recycledback to the liquid phase reactor to aid in mixing, pressure maintenance,and product carrier.

EXAMPLE 3

A 2000 gallon commercial scale reactor is charged with antimonypentachloride catalyst. HCFO-1233xf and HF are fed continuously to thereactor vessel. HF is fed in excess. Hydrogen chloride is added as anadditional component to aid mixing and to aid in volatilizing theproduct. HCFC-244bb, HF and hydrogen chloride exit the vessel and arerecovered.

EXAMPLE 4

This example illustrates the continuous vapor phase fluorinationreaction of 1,1,2,3-tetrachloropropene(TCP)+3HF→2-chloro-3,3,3-trifluoropropene (HCFO-1233xf)+3HC1. Thefluorination catalyst for the experiment was fluorinated Cr₂O₃.

A continuous vapor phase fluorination reaction system consisting of N2,HF, and organic feed systems, feed vaporizer, superheater. 4″ ID Monelreactor, acid scrubber, drier, and product collection system was used tostudy the reaction. The reactor was loaded with 9415.2 grams ofpretreated Cr₂O₃ catalyst which equates to about 6.5 liters of catalyst.The reactor was then heated to a reaction temperature of about 235° C.with a N2 purge going over the catalyst after the reactor had beeninstalled in a constant temperature sand bath. The reactor was at about3 psig of pressure. 11F feed was introduced to the reactor (via thevaporizer and superheater) as a co-feed with the N2 for 15 minutes whenthe N2 flow was stopped. The HF flow rate was adjusted to 1.4 lb/hr andthen 1,1,2,3-tetrachloropropene (TCP) feed was started to the reactor(via the vaporizer and superheater). The feed rate of TCP was keptsteady at about 0.8 lb/hr and HF feed was kept steady at 1.4 lb/hr forabout a 15 to 1 mole ratio of HF to TCP. Once the reaction started thecatalyst bed temperature rose to a range of 250-260° C. The contact timeat 250-260° C., 3 psig and the above feed rates was calculated to beabout 16 s. The average composition of the material that was collectedover 500 hours of on-stream time was about 97.2 GC area % HCFO-1233xf,1.6 GC area %244bb, 0.6 GC area % HFO-1234yf/HFC-245cb, 0.1 GC area %HCFC-1223xd, and 0.08 GC area % HCFO-1231xf. After 500 hours an underfluorinated intermediate, 2,3-dichloro-3,3-difluoropropene (HCFO-1232xf)started to appear as the selectivity to HCFO-1233xf decreased when thecatalyst started losing activity. When the selectivity to HCFO-1233xfdecreased to about 83% after 650 hours of on-stream time the reactionwas stopped due to loss of catalyst activity. The conversion of TCPremained at >99% throughout the run.

EXAMPLE 5

The reactor effluent from the reaction described in Example 4 is fed toa conventional distillation column where HCl distillate is recovered.The distillation column bottoms mainly contains unreacted HF andHCFO-1233xf and are fed forward for additional processing/purification.The HCl that is recovered, in whole or in part, is then used as thesource of the co-fed HCl, to the liquid phase reaction system asdescribed in Example 1.

While the present invention has been particularly shown and describedwith reference to preferred embodiments, it will be readily appreciatedby those of ordinary skill in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe invention. It is intended that the claims be interpreted to coverthe disclosed embodiment, those alternatives which have been discussedabove and all equivalents thereto.

What is claimed is:
 1. A process for the production of2-chloro-1,1,1,2-tetrafluoropropane which comprises reacting2-chloro-3,3,3,-trifluoropropene with hydrogen fluoride, in a liquidphase reaction in the presence of hydrogen chloride and a liquid phasefluorination catalyst, wherein the hydrogen chloride is added into thereaction from an external source at a pressure of about 100 psig ormore.
 2. The process of claim 1 wherein the reacting is conducted in aliquid phase reaction vessel.
 3. The process of claim 1 wherein thereacting is conducted continuously.
 4. The process of claim 1 whereinthe mole ratio of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropenefed to the reaction ranges from at least 1:1 to about 50:1.
 5. Theprocess of claim 1 wherein the mole ratio of hydrogen chloride to2-choro-3,3,3-trifluoropropene fed to the reaction ranges from at least0.1:1 to about 10:1.
 6. The process of claim 1 wherein the liquid phasefluorination catalyst comprises SbCl₅, SbCl₃, SbF₅, SnCl₄, TaCl₅, TiCl₄,NbCl₅, MoCl₆, FeCl₃, CrF₃, Cr₂O₃, a fluorinated species of SbCl₅, afluorinated species of SbCl₃, a fluorinated species of SnCl₄, afluorinated species of TaCl₅, a fluorinated species of TiCl₄, afluorinated species of NbCl₅, a fluorinated species of MoCl₆, afluorinated species of FeCl₃, a fluorinated species of Cr₂O₃, orcombinations thereof.
 7. The process of claim 1 wherein the reacting isconducted at a temperature of from about 30° C. to about 200° C.
 8. Theprocess of claim 1 wherein the reacting is conducted at a pressure offrom about 5 psia to about 200 psia.
 9. The process of claim 1 furthercomprising the step of recovering the hydrogen chloride.
 10. The processof claim 1 wherein the 2-chloro-3,3,3,-trifluoropropene is produced by aprocess comprising fluorinating 1,1,2,3,-tetrachloropropene.
 11. Theprocess of claim 10 wherein the 1,1,2,3,-tetrachloropropene isfluorinated with hydrogen fluoride and the reacting thereby produces anintermediate stream comprising hydrogen fluoride,2-chloro-3,3,3,-trifluoropropene and hydrogen chloride.
 12. The processof claim 11 further comprising the step of recovering the hydrogenchloride.
 13. The process of claim 12 wherein at least a part of therecovered HCl stream is directly fed to the liquid phase reactor.